A SMALL GLACIAL CIRQUE BASIN ON EXMOOR, SOMERSET

Geomorphological and sedimentological investigations Lit the Punchbowl on Exmoor, north Somerset, have demonstrated evidence of cirque basin glaciation, some 30 km south of the accepted southern limit of Anglia n ice cover in this area, The Punchbowl is a steep-sided, north-facing basin that has a subdued arcuate ridge at its mouth. Analysis of macr ofabrics, clast form and roundness and particle size on sediments form ing the ridge indicate it to consist of glacial diamict deposited as a terminal moraine, Further evidence supporting the presence of a forme r cirque basin glacier at this site is derived from basin morphology a nd a striated sandstone boulder Palaeoglacier reconstruction gives a s urface area of 0.38 km(2), a maximum thickness of 46.5 m and a maximum basal shear stress value of 51 kPa. The ELA of the Former glacier has been calculated at 334 m OD. There is no evidence for multiple glacia tions at this site, and, in the absence of dating controls on the mora ine. the glacier is provisionally assumed to have formed during severe climatic conditions associated with the southerly advance of ice shee ts during the Anglian cold stage or during the Dimlington Stadial. Dev elopment of a glacier at this location appears to have been a rare eve nt during the Quaternary, and map have been facilitated by accumulatio n of windblown snow from the adjacent plateau.